The current names come from the Vikings. Norse custom was to name a thing as they saw it. For instance, when he saw wild grapes (blackberries, probably) growing on the shore, Erik the Red’s son, Leif Eríksson, named a portion of Canada “Vinland.”
Ice core and mollusk shell data suggests that from A.D. 800 to 1300, southern Greenland was much warmer than it is today. This means that when the Vikings first arrived, the Greenland name would make sense. But by the 14th century, maximum summer temperatures in Greenland had dropped. Lower temperatures meant fewer crops and more sea ice, forcing the local Norse population to abandon their colonies.
The Icelandic sagas fill in the other half of the switched-name story.
(The final comment from the author tries to tie in climate change, but actually disproves manmade climate change and favors the fact that climate does indeed change over a long period of time.)
Unfortunately, the Land of the People Most Adept at Living With Ice now faces the impending realities of climate change. The rapidly melting Greenland ice sheet has resulted in cold temperatures in the North Atlantic, which has significantly slowed the Gulf Stream. Should the trend continue, Iceland will likely suffer much colder temperatures and even sea ice, while Greenland will continue to grow warmer and shed icebergs at an alarming rate.
In a century or two, it could very well be that the globe will make more sense, and Iceland and Greenland will better resemble the names they were given a thousand years ago.
https://www.nationalgeographic.com/news/2016/06/iceland-greenland-name-swap/
Didn’t the last surviving Norse colonists pull out about the time of Columbus?